Rotary magnetic actuators



Feb. 3, 1959 A. J. BUCHTENKIRCH 2,872,628

ROTARY MAGNETIC ACTUATORS Filed Dec. 28, 1954 E 5 :E I INVENMR] ARTHURJ. BUCHTENKIRCH United rates Fatent @ffice 2,872,628 Patented Feb. 3,1959 has ROTARY MAGNETIC ACTUATORS Arthur J. Buchtenkirch, Glen Cove, N.Y., assignor to North Atlantic Industries, Inc., Glen Cove, N. Y.

Application December 28, 1954, Serial No. 478,059 Claims. (Cl. 317-197)This invention relates to a rotary magnetic actuator and moreparticularly, to an electromagnetic device which rotates a shaft througha limited angle with or without an applied load.

A device of this character is suitable for providing a power outputwhich can be used for a large number of electrical and mechanicalpurposes, and as, for example, to operate switches, valves, clutches,latches or the like.

it is a primary object of this invention to provide a structure,inexpensive in construction, which is capable of converting a maximumamount of electrical energy into delivered torque.

In addition it is an object of my invention to provide a device whereinmaximum starting torques are made available at the output shaft duringany of the operations of this device.

A further object is to provide an actuator having a shaft which may bothdeliver a turning torque and which may be axially moved to deliver alimited axial thrust.

In order to accomplish my objectives, I provide a magnetic structurehaving pole pieces with inclined faces. Cooperating with these faces isan armature rigidly mounted upon a rotatable shaft. The armature isspaced from the faces by an air gap and adapted to move to reduce thisair gap when the magnetic structure is energized. In addition, the polepiece faces are located on one side of the armature, so that thearmature may be axially moved as the air gap is closed thereby impartinga limited axial movement to the shaft.

These and other objects and advantages will become apparent upon readingthe following description of which the attached drawings form a part.

Referring to the drawings:

Figure 1 illustrates an exploded view, with parts omitted, of the basicform of my invention.

Figure 2 is a cross-sectional view of the device of Figure 1 in itsoperative condition.

Figure 3 is a modification of Figure 2, and illustrates a second type ofcoil winding, and

Figures 4 and 5 each show an exploded view of a modification.

This device is essentially a limited rotation mechanism wherein anarmature fixed to an output shaft will rotate until the armature andpole pieces interfere with one another or until a mechanical stop meansis operated.

In Figures 1 and 2, I illustrate a construction which shows theapplication of my invention. In this construction, a magnetic structure1, is formed with a pair of pole pieces 2 and 3. An opening 4 isprovided in the magnetic structure through which a rotatable shaft 5 isinserted. Surrounding a portion of the shaft and fixed to the magneticstructure is a bushing 6. The bushing and the shaft, in this case, arepreferably formed of a magnetic material to complete the magneticcircuit.

An armature 7, is provided with a central opening through which shaft 5is placed. The armature and shaft are rigidly secured together as bywelding or any suitable mechanical fastening means.

The armature itself, is formed of a fiat plate of magnetic materialwhose ends or arms 8 and 9 are twisted into a so-called butterfly formfor reasons to be set forth hereunder.

As can be seen in the illustration of Figure 1, the pole pieces 2 and 3which are substantially parallel to the axis of the shaft are providedwith faces 11 and 12 which faces are inclined at an angle to the axis ofthe shaft. The twisted arms of armature 7 are so made that the portionoverlapping the pole piece faces, hereinafter referred to as armaturefaces, are either parallel or non parallel to the plane of the polepiece faces. The selection of parallelism or non-parallelism will dependon the application to which the device is to be put as will becomeapparent hereafter.

The armature is normally positioned so that a portion of its facesoverlap a portion of the pole piece faces. However, these faces arepreferably separated by an air gap even when they fully overlap. Thus,when a coil winding 13 is electrically energized the pole pieces becomemagnetized and the lines of flux pass from one pole piece through itsrespective armature arm and then to the second pole through itsrespective armature arm. In this situation the armature tends to reduceor close the air gaps and the armature thereby rotates.

Where the pole piece and armature faces are parallel rotation stops atthe point of minimum air gap. When the faces are non-parallel, rotationstops when contact is made between these faces. In either case, however,a mechanical stop (not shown) may be provided to stop rotation at anypredetermined point. To return the armature to its normal position whenthe coil is de-energized, a spring 14 or some other suitable mechanicalmeans may be provided.

The angle of inclination of the pole piece and armature faces is chosenin accordance with the speed of rotational response desired and inaccordance with the amount of rotation desired. in addition, the angleis also chosen to maximize the torque versus power input characteristic.It is to be noted that an angle which will increase the torque willdecrease the time for a given rotation. However, the time constant ofthe actuator is unchanged.

in the modification of Figure 3, I show a construction similar in allrespects to Figures 1 and 2, with the exception that the single coilwinding is replaced by a pair of coils 15 and 16 wound around themagnetic structure at the base of the pole pieces. It is thus apparentthat the design of and the type of coils used may be varied considerablyto obtain varying results from the device.

in Figure 3, the shaft 5 and bushing 6 may be made of either a magneticor non-magnetic material. If the shaft and bushing are nonmagnetic thenthese elements will not be included in the magnetic circuit and the twocoils will oppose one another.

In Figure 4, a device similar to Figs. 1 and 2 is shown. However, here,the pole piece faces are grooved or channelled at 18 to support one ormore ball bearings 19 These ball bearings ena le the rotating armatureto lift the shaft upwardly (in Fig. 4) as the armature faces move overthe pole piece faces. Consequently, in this type design, not only doesthe shaft rotate but it also moves axially to a limited degree. Thisfeature may be utilized in various mechanical applications of thisdevice.

Other type bearings may also be used, as for example rollers or a solidsheet of non-magnetic material secured to the faces of the pole pieces.In Fig. 4, the pole piece and armature faces are preferably non-parallelso that movement of the armature over the pole piece causes the armatureto lift away from the pole piece face. By properly shaping the angularair gap, a constant axial force is obtained with armature rotation.

The device as described is a D. C. unit. Where it is aeraees desired touse A. C. power, it is preferable to use a laminated" magnetic structureand a laminated armature to reduce eddy current losses. Thus, in Figure5, 1 show a laminated magnetic structure and a laminated armatore 2ft;similar'otherwise to the magnetic structure and armature of Figure l;

In addition, in order to avoid objectionable vibrations, a pole shaderis used in this construction. For example, the pole pieces 22. and 23are grooved at 24 and 25 and a solid turn of copper 26 or other suitablematerial encircles that portion of the'pole piece locate between thegrooves. I

in this illustration as in the illustration of l 'igure 4, the coilWinding has beenomitted to simplify the drawings.

By means of my invention, maximum desired starting torques may beobtained for any desired application, due to the flexibility ofdesign ofthe various face angles. Moreover, because of the low armature inertiaand because the magnetic structure produces a turningtorqueuponthearmature, a minimum amount of energy is required to produce shaftrotation.

This invention may be developed within the scope of the following claimswithout departing from the essential features of said invention.Accordingly, it is desired that the foregoing description be read asshowing several operative embodiments of said invention and not in astrictly limiting sense. i

I claim: 7

l. A rotary magnetic actuator comprising a magnetic structure formed ofa thin, fiat, elongated plate of magnetizable material, having itsopposite ends bent substantially normal to the plate to form a U-shape,with the legs of the U forming flat pole pieces which are spaced apart aconsiderable distance and with the planes of the legs beingsubstantially parallel, the plate portion forming the base of the Ubeing centrally apertured and a rotatable shaft extending through theaperture and between the pole pieces and being equidistantly spaced fromand parallel to the pole pieces; the ends of each of the pole piecesbeing sloped, relative to the plane of the plate portion forming thebase of the U, to form inclined pole faces facing away from the bottomof the U and with the slope of one pole face being opposite to that ofthe other pole face; and an armature consisting of a thin, flat platecentrally secured to the shaft to rotate therewith and having endsarranged to overlap the pole faces with these overlapping ends beingtwisted to slope at approximately the same angle as the slope of theirrespectively overlapped pole faces; and means to magnetize the polepieces.

2. A rotary magnetic actuator comprising a magnetic structure formed ofa thin, flat, elongated plate of magnetizable material, having itsopposite ends bent sul stantially normal to the plate to form a U-shape,with the legs of the U forming flat pole pieces which are spacedapart aconsiderable distance and with the legs being substantially parallel; ashaft rotatably mounted between the pole pieces and being equidistantlyspaced from and parallel to the pole pieces; the ends of each of thepole pieces being sloped, relative to the plane of the plate portionforming the base of the U, to form inclined pole faces facing away fromthe bottom of the U and with the slop e of one pole face being the sameas, but oppositely inclined relative to the other pole face; an armatureconsisting of a fiat, thin, plate centrally secured to the shaft forrotation therewith and having opposite portions which are arranged toextend over and overlay the pole faces, with these armature portionseach being twisted to slope at approximately the same angle as the slopeof their respective overlapped pole face, and a magnetic coil positionedbetween the two pole pieces and between the armature and the U base andwith the coil surrounding the shaft. a

3. A rotary magnetic actuator comprising a magnetic structure formed oftwo fiat, thin, relatively narrow magnetizable plates arranged parallelto one another and spaced apart a considerable distance and having lowerends which are interconnected by a flat, thin bottom plate and upperends which form pole faces facing away from the bottom plate and withthe upper end pole faces being sloped in the planes of the pole'piecesrelative to the bottom plate; a shaft centrally located between the polepieces and arranged parallel thereto, an armature in the form of a flat,thin narrow plate, centrally connected to the shaft and located abo vethe pole faces and with the two ends of the armature plate radiallyextending from the shaft a sufficient distance to each overlap one ofthe pole faces, with the overlapping portions of the armature platebeing twisted to slope in substantially the same direction and degree asthe pole face they respectively overlap, and means for magnetizing saidpole pieces.

4. A construction as defined in claim 3 and wherein the means formagnetizing said pole pieces includes an electrical coil arrangedbetween the pole pieces, above the bottom plateand below the armatureand surrounding the shaft.

5. A construction as defined in claim 3 and with the slope of thetwisted overlapping portions of the armature plate being such that suchoverlapping portions contact their respective pole faces upon rotationof the armature and shaft relative to the pole pieces to a point wherethe armature overlapping portions substantially overlap their respectivepole facesQ i References Cited in thefile ofthis patent UNITED STATESPATENTS 541,471 Corey June 25, 1895 Walker July 7, 1942.

